Torsionally rigid, elastically flexible shaft coupling

ABSTRACT

In a torsionally rigid, elastically flexible shaft coupling having at least one elastic disk disposed at right angles to the axis of rotation, cams on both coupling halves act alternately on both sides of the disk. In order to improve the loading capacity of the connection of the disk with the cams of both coupling halves by a multi-section design of this connection and in order to increase the transmitting capacity and the flexibility, the shaft coupling has the following characteristics: 
     (a) the disk is constructed as a ring, 
     (b) the points of application of the cams of both coupling halves on the annular disk lie at least approximately on one radius, the said cams surrounding the annular disk on both sides.

The invention relates to a torsionally rigid, elastically flexible shaftcoupling having at least one elastic disk disposed at right angles tothe axis of rotation on which cams of both coupling halves act.

Such a shaft coupling is known from German Gebrauchsmuster No. 73 21095. There a disk made of stratified membranes is used as an elastictransmission element between two coupling halves. Cams on one couplinghalf act on both sides from the inner edge of the membrane package. Hereone cam is constructed as a collar on the coupling half, while the othercam, designed as an annular disk, sits torsionally rigidly on a journalof this coupling half. The cams of this coupling half and the membranepackage are frictionally and form-locking connected by means ofthrough-screws. In this way a double-shear fastening of the membranepackage to this coupling half is achieved.

The outer edge of the membrane package of the known shaft coupling issurrounded by cams of the other coupling half. The connection betweenthese cams and the membrane package is produced here by rivets. However,because only the cams acting on one side of the membrane package areconnected in a torsionally rigid manner to the assigned coupling half,there is only single-shear fastening of the membranes to the couplinghalf. By the double-shear fixing at the inner edge and the single-shearfixing at the outer edge of the membrane package, allowances are madefor the variable large forces acting on various radii. However there isunharmonic transmission of the forces between their points ofapplication on the membrane package. The membrane package, which istangentially stressed thereby, is overdimensioned in its cross-sectionwith regard to the lower forces acting on the outer edge of the membranepackage. This, however, results in a higher bending resistance for themembrane package.

The object of the invention is to increase the loading capacity of ashaft coupling with improved flexibility.

This object is solved in the present invention by providing a flexibleannular elastic disk or ring and arranging the points of application orfastening of the cams of both coupling halves which enclose both sidesof the ring to lie at least approximately on one radius.

The solution is advantageous insofar that a torque is transmitted byforces from the cams of one coupling half to the flexible annular diskand from this to the cams of the other coupling half on one radius. Theforces acting at the points of application of the cams are therefore thesame size and the annular disk is subject to substantial compressionstress and tensile stress. On the basis of this regulated transmissionof force, the annular disk is uniformly stressed, so that, in comparisonwith the state of the art, it can have a smaller cross-section with thesame transmitting capacity and improved flexibility. The transmittingcapactity of the coupling is substantially increased in comparison withthe known design by the multi-shear fixing of the cams of both couplinghalves to the elastically flexible annular disk on a comparatively largeradius.

Advantageous refinements of the invention are described below.

The cams of one coupling half are formed as radially inwardly extendingtongue-like plates that extend inward from the external mountingperiphery of the one coupling half. The cams of the other coupling halfare formed as radially outwardly extending tongue-like plates thatextend outwardly from the internal mounting periphery of the othercoupling half. The tongue-like plates overlap, in the direction of therelated coupling half, into a closed circular ring concentric to theaxis of rotation. This ensures that cams are very strong whilesimultaneously decreasing their mass enabling them to surround theannular disk on both sides.

Additional refinements of the invention may be included to increase themultiple-shearing of the connection between the annular disks or annulardisk packages respectively and the cams. Such refinements may includeproviding at least two annular disks and having one cam of each couplinghalf disposed between individual disks. Also, annular disks may bearranged in packages and the coupling halves may act on both sides, atthe front of the individual disk packages.

Cams may be provided which act at a smaller radius on the associatedcoupling half than on the annular disks, and those cams interlock withtheir respective coupling half by toothing between them. This ensuresthe transmission of particularly high forces onto a small radius.

The plates of both sets of cams and the annular disk(s) may bepenetrated by a shoulder sleeve in which one screw braces the plates andcomes between the shoulder of the sleeve and the disk. This operates todecrease the notch effect between the cams and the annular disk(s) if apart of the torque is transmitted form-locking when the frictionalcontact is exceeded.

Two exemplified embodiments of the invention are explained in moredetail below by the means of drawings. They show:

FIG. 1 a cross-section through a shaft coupling disposed between twocoupling halves as the first exemplified embodiment, the said shaftconsisting substantially of cams for the two coupling halves and annulardisks disposed between them as the elastic transmission element.

FIG. 2 a view seen in the direction of arrow II in FIG. 1 of one camrespectively of the corresponding coupling half having an interposedannular disk, on a smaller scale than in FIG. 1, and

FIG. 3 a cross-section of a similar shaft coupling, having only oneannular disk, as the second exemplified embodiment, in which the camsare also connected to the inner coupling half in a form-locking manner.

FIG. 4 is a fragmentary cross-section of FIG. 3, showing an alternateembodiment.

The first exemplified embodiment, shown in FIGS. 1 and 2, of atorsionally rigid, elastically flexible shaft coupling 10, has acoupling half 11 having a flange with a large diameter. Three cams 13,14 and 15 are congruently attached to this flange 12 on the front side.As FIG. 2 shows on the left with the example of cam 14, the cams 13, 14and 15 are constructed as closed rings 17 passing concentrically to theaxis of rotation 16 of the shaft coupling 10. From these proceed threetongue-shaped plates 18 extending radially against the axis of rotation16 with uniform spacing of 120°. The two cams 13 and 15 are of the samethickness both in the region of the ring 17 and also of plates 18. Thering 17 of the cam 14 is strengthened in its cross-section on both sidesof its plate 18, so that there remains a gap of corresponding thicknessbetween the plates 18 of the stacked cams 13 to 15. However, deviatingfrom the exemplified embodiment described, the cam 14 may also consistof one or two cams 13 or 15 with a similar shape, to which spacer ringsof corresponding width are attached. The cams 13 to 15 are connected tothe flange 12 of coupling half 11 by means of through-screws andtight-fit screws 19.

The second coupling half 20 of the shaft coupling 10 has a flange 21with a smaller diameter than that of the other coupling half 11. To theflange 21 are attached cams 22, 23, and 24 which are congruent anddisposed concentrically to the axis of rotation 16. The cam 24, shown onthe right in FIG. 2, of coupling half 20 has a closed annular shape 25,from which issue three plates 26 passing radially outwards with uniformspacing of 120°. The two other cams 22 and 23 are also designedaccordingly. The cams 22 to 24 are screwed in a torsionally rigid mannerwith through-screws and tight-fit screws 27 to the flange 21 of couplinghalf 20.

As FIG. 1 clearly shows, the plates of cams 13 to 15 and 22 to 24, whichextend in the same radial plane respectively, have a cross-section ofthe same width. Moreover, the plates 18 and 26, mutually offset in theperipheral direction by 60°, of the respectively assigned cams 13 and 22or 14 and 23 or 15 and 24 respectively of the two coupling halves 11 and20 interlock with mutual play, as shown on the left in FIG. 2 by thedash-dot line in a simplified way for cams 14 and 23.

Elastic annular disks 28 are inserted as transmission elements for thetwo coupling halves 11 and 20 between plates 18 and 26 respectively ofthe corresponding cams, the cross-sections of said plates beingadjacent. The thin-walled annular disks 28 are essentially ring-shaped(FIG. 2). They are provided with groups of three bores 29 with a spacingof 60°. Between these groups of bores 29 the cross-section of theannular disks 28 is radially tapered. The groups of bores 29 lying on anaverage radius r are also present in plates 18 and 26 of cams 13 to 15and 22 to 24. The bores 29 receive through-screws 30 for the torsionallyrigid connection of the annular disks 28 to the cams 13 to 15 and 22 to24 of the two coupling halves 11 and 20, in each bore group respectivelyat least one screw being constructed as a tight-fit screw or beingsurrounded by a fitted sleeve (not shown). Here washers 31 designedaccordingly are inserted on both sides of the annular disks 28 (blackcross-sections in FIG. 1). These may consist of a material having asmaller E modulus than the annular disks. They may be connected to theannular disks by glueing or soldering to reduce the clamping notcheffect. Instead of the washers, the annular disks in the clamping areamay also be strengthened axially with a gradual transition to theelastically flexible area (not shown).

In the second exemplified embodiment of a shaft coupling 40 shown inFIG. 3, only two cams 43 and 44 are fastened with plates 45 to its onecoupling half 41 at the flange 42 having a large diameter. These camscorrespond to cams 13 and 15 of the first exemplified embodiment.Between the cams 43 and 44 is inserted a spacer ring 46. These threecomponents are held by means of screw connections 47 to the flange 42 byfriction contact.

Two cams 51 and 52 having plates 50 and with an interposed spacer ring53 are fastened to the small-diameter flange 48 of the other couplinghalf 49 by means of screw connections 54. The cams 51 and 52 correspondto the external cams 22 and 24 of the first exemplified embodiment. Asthe fastening of the cams 51 and 52 to the flange, which is to beregarded as single-shear, occurs on a relatively small radius, in somecircumstances the friction contact achieved by the screw connection 54may not suffice for the transmission of a high torque. Therefore in theregion of the cams 51 and 52, the coupling half 49 is provided withexternal toothing 55, and the cams are each provided with internaltoothing 56 on their inner edge. This toothing is in the form of a gearwheel. This additional form-locking may also be achieved by radialserrations on the front sides of the cam 52 and of the flange 48 of thecoupling half 49 turned towards one another (not shown). Furthermore,fitted bolts, cylindrical pins, etc are suitable as further form-lockingelements connecting the cams of both coupling halves with the respectivecoupling flange. An increase in the transmitting capacity is possible byimproving the friction contact, e.g. by means of a flat thread orsuitable profiling of the components assigned to one another.

Between the plates 45 and 50 of the cams 43, 44 and 51, 53 of bothcoupling halves 41 and 49, which are in the same respective planes, isinserted as a transmission element just one elastic annular disk 57,which corresponds to one of the disks 28 of the first exemplifiedembodiment. By this the shaft coupling 40 is more flexible than such acoupling having transmission elements disposed with mutual axialspacing. However, a package of annular disks (shown in FIG. 4) may alsobe used instead of an annular disk.

The annular disk 57 is connected in the peripheral direction alternatelywith the plates 45 of the cams 43, 44 or plates 50 respectively of cams51, 52 by interposing washers 58 (black cross-section). For this purposethese components are penetrated by one shoulder sleeve 59 respectively,which engages with its end section turned away from the shoulder in adisk 60. The shoulder sleeve 59 and the disk 60 are braced by a screw 61to achieve the required friction contact between the cams 43, 44 or 51,52 respectively and the annular disk 57. Instead of the connectiondescribed, a screw coupling formed by a tight-fit pin with a nut mayalso suffice.

The shaft coupling according to the invention may also be provided witha larger number of annular disks 58A and 58B, shown in FIG. 4, incontrast with the two exemplified embodiments. These may be inserted asa package layered between the plates of the cams. With the arrangementof a larger number of annular disks or annular disk packages with mutualspacing, the number of cams is to be increased accordingly by onebetween each pair of disks. Plates or packages of plates, which arecombined to form a ring, may also be used as transmission elements.

What is claimed is:
 1. A torsionally rigid, elastically flexible shaftcoupling comprising: a first and a second coupling half;at least oneannular elastic disk arranged between the coupling halves at a rightangle to the axis of rotation of the coupling; a respective plurality ofcams affixed to each of the coupling halves and being formed withradially extending tongue-shaped protruding plates, the cams of eachcoupling half being arranged to enclose both axial sides of the annulardisk; the tongue-shaped protruding plates of each cam affixed to onecoupling half being arranged in intermeshing radial alignment with theprotruding plates of a corresponding cam affixed to the other couplinghalf so that the protruding plates are fastened to the disk at arespective plurality of circumferential locations around the disk atleast approximately on a single radius; the cams of one of the couplinghalves extending, from their respective locations of fastening on theelastic disk, radially inwardly to a first closed circular ringconcentric with the axis of rotation and disposed radially inwardly ofthe space defined by the annular disk; the cams of the other couplinghalf extending, from their respective locations of fastening on theelastic disk, radially outwardly to a second closed circular ringconcentric with the axis of rotation and disposed radially outwardly ofthe space defined by the annular disk.
 2. Shaft coupling according toclaim 1, having at least two annular disks and one cam respectively ofboth coupling halves being disposed between the individual annulardisks.
 3. Shaft coupling according to claim 1, wherein each annular diskis an annular disk package of parallel elastic disks.
 4. Shaft couplingaccording to claim 1, wherein the cams of the one coupling half includeform-locking means at the inner periphery thereof for engagingform-locking means on the one coupling half.
 5. Shaft coupling accordingto claim 1, further comprising a shoulder sleeve penetrating the platesof the cams and the annular disks, and a screw for bracing the camsbetween the shoulder of the sleeve and the disk.